People using cellular telephones have become so common that they scarcely warrant attention. The cellular telephone has become a part of America's pop culture. Individuals push shopping carts through the aisles of the local supermarket while carrying on a conversation with friends (who, perhaps, are also talking on a cellular phone) and we regard it as normal behavior. Cellular telephones have become so pervasive that new etiquette rules regarding acceptable behavior in using cellular telephones continue to develop. It is no longer considered proper, for instance, to carry on a cellular phone conversation in a restaurant where it will disturb nearby diners. Likewise, some consider using a cellular phone while driving to constitute behavior as hazardous to others as that of drinking alcoholic beverages and then driving an automobile.
In addition to securing a place in pop culture, the cellular telephone and similar devices, such as pagers and portable computers, have dramatically impacted modern business practices. The fact that people have nearly constant contact with each other has shortened the time within which business transactions can be completed. The pervasiveness of pagers, cellular telephones and modem equipped portable computers has raised the expectations of people who expect to be able to establish contact with, and be contacted by, anyone at nearly any time. We are reminded of this every time we see a person sending or receiving email on a portable computer while waiting for an airplane or when we see people using their cell phone to check for messages or return phone calls during intermission at the theater or a break in a seminar.
Although cellular phones, pagers and portable computer modems have given us the capability to be in contact nearly everywhere at any time, the usefulness of such devices is limited by the devices' power supply. Other portable electronic devices, such as answering machines, cordless telephones and video cameras, also have the same limitation. The majority of such devices use a DC battery power supply. In some cases the device is powered by disposable batteries, while other devices are powered by a rechargeable battery or batteries. In most higher end devices, such as portable computers or cellular telephones, a rechargeable battery is used.
Rechargeable batteries used in cellular telephones and portable computers generally can be used for limited number of hours before the battery or batteries must be recharged. The ability of the battery being able to accept and retain a charge is limited by the length of time the battery has been in use and the number of recharging cycles that the battery has undergone. With the passage of time, the capacity or ability of a battery to hold a charge diminishes due to battery deterioration. Similarly, each time a battery is recharged, its capacity to hold a charge is slightly diminished from the charge it could hold before the preceding recharging cycle. This means that an older battery or one that has been through a number of recharging cycles, or both, although it can be fully charged, will lose its charge much faster than a newer battery or one that has not gone through a number of recharging cycles.
In most cases, the user of a cellular telephone or portable computer does not notice the gradual deterioration of battery capacity that is taking place. This lack of awareness can place a user in the awkward position of having his or her cell phone cease operation in the middle a phone call or a computer having to be shut down at a critical time. It can mean that a fully charged video camera will prematurely cease to operate during an important personal event, such as a wedding, a child's soccer game or a piano recital.
In many such instances the user of the device may have started out with a fully charged battery, but had no indication of the capacity of the battery to hold the charge. Even if the user has a replacement battery, the cell phone, computer, or video camera, as the case may be, must be stopped while the battery is being replaced. If the user does not have a replacement battery, he or she must wait until they can procure one or they have access to AC power so they can either recharge the weak battery or operate the device off its charging device. If the user of the cell phone, computer, video camera or other battery powered device had an indication of the true capacity of the battery before hand, he or she may have been able to plan accordingly by either minimizing use of the device or by replacing the battery with one having an acceptable remaining capacity.
Accordingly, what is needed in the art is a device and method to calculate the remaining capacity of a battery so a user of a battery powered device knows when he or she should replace the battery.